Today more than ever before, electronics designers must pack higher powered components closer together in ever-smaller spaces. More power in less space translates to increased power densities, and higher device operating temperatures, thereby requiring increased heat dissipation. As temperatures rise, the reliability and functionality of electronic components are impaired dramatically. Experience has shown that more than 50 percent of electronic failures are the result of thermal problems. Traditionally, heatsinks are used to transfer heat from components generating the heat to an area where the heat can be dissipated (such as the atmosphere) or adequate ventilation is provided to remove the heat from the heatsink.
Most conventional heatsinks use some form of mechanical method to attach the heat-generating component to the heatsink. The most common methods are: adhesives, spring clamping devices, or holddown brackets/clamps with a mechanical fastener, such as a machine screw. Adhesives have well known disadvantages associated with storage and handling. In those cases not employing adhesives, the heatsinks are usually made of two pieces: a main heatsink body, and a separate retaining clamp. The clamp is usually secured to the main body by a machine screw or stud and nut.
Special problems arise when multiple components, such as field effect transistors (FETs) and diodes, are attached to a single heatsink. Referring initially to FIG. 1A, illustrated is an exploded isometric view of one example of a conventional approach to mounting multiple components to a single heatsink. In this approach, mounting apertures 115, 125, 135 of three individual components 110, 120, 130, respectively, are located as provided by their manufacturer(s) near the top 113, 123, 133 of each component 110, 120, 130. First, second and third threaded mounting studs 145a, 145b, 145c may be mounted on a conventional heatsink 140 such that the threaded mounting studs 145a, 145b, 145c may be passed through the individual mounting apertures 115, 125, 135. In an alternative embodiment, the threaded mounting studs 145a, 145b, 145c may be replaced with machine screws (not shown). The components 110, 120, 130 are secured with hex nuts 147.
One skilled in the art will readily recognize that a mounting force applied to the mounting apertures 115, 125, 135 located near the top 113, 123, 133 of the components 110, 120, 130 will not apply uniform mounting pressure to the components 110, 120, 130, thus increasing interfacial thermal resistance. Plastic washers (not shown) are optionally needed in many cases to electrically isolate the mounting studs 145a, 145b, 145c. Also, when the components 110, 120, 130 are used on a primary circuit board (not shown) of a power unit, arcing can occur between the component mounting apertures 115, 125, 135 surface and the mounting studs 145a, 145b, 145c or heatsink 140 due to the high voltage potential and the small spacing distance.
An alternative conventional system for mounting three heat-generating components is illustrated in FIG. 1B. Rather than mounting each component 110, 120, 130 individually as in FIG. 1A, two non-symmetrical brackets 150, 160 clamp the first, second and third components 110, 120, 130 to the heatsink 140. The non-symmetrical brackets 150, 160 include bracket mounting apertures 155, 165 that cooperate with the threaded mounting studs 145a, 145b and hex nuts 147 to secure the components 110, 120, 130 to the heatsink 140. The non-symmetrical brackets 150, 160 further include raised bosses 157a, 157b, 167a, 167b (toward the components 110, 120, 130) designed to make contact with the components 110, 120,130. This approach does not work well when the center component 120 is small, e.g., a TO220 (JEDEC outline) package size in relation to the end (first and third) components 110, 130. The raised bosses 157b, 167b may miss the component 120 or strike an edge 123, 124 of the component 120 cracking the component housing and causing component failure. Of course, the components 110, 120, 130 might be relocated to achieve a better clamping profile. That would, however, require redesign of the circuit traces on a printed wiring board (not shown) at a significant cost.
A third conventional approach for mounting three heat-generating components is illustrated in FIG. 1C. In this instance, two spring steel clamps 170, 180 include mounting apertures 175, 185 therethrough and projections 177, 187. This approach accommodates the varying thicknesses of the components 110, 120, 130, but has a limitation on a clamping force that may be exerted on the components 110, 120, 130. It is well known in the art that increasing the contact pressure (clamping force) decreases the interfacial thermal resistance between the components 110, 120, 130 and the heatsink 140. Clamps 170, 180 of this type are well known to deform under the pressure exerted during torquing of the nuts 147.
Thus, the aforementioned and other currently existing clamp assemblies have not been able to adequately accommodate multiple components for attachment to a heatsink. Accordingly, what is needed in the art is a low-cost, easy-to-manufacture, and easy-to-assemble clamp that facilitates attachment of multiple and, in many instances, different size components to a single heatsink.